The present invention relates to a toner for use in a recording method utilizing electrophotography, electrostatic recording, electrostatic printing, or toner jetting; and also an image forming method and a process cartridge using the toner.
In electrophotographic processes in general, an electrostatic image is formed by various means on a photosensitive member comprising a photoconductive substance and developed with a toner to form a toner image. The toner image is then transferred onto a transfer(-receiving) material, such as paper, and fixed by application of heat; pressure, or heat and pressure, or with solvent vapor to provide an image product, such as a print or a copy.
Development methods adopted in electrophotography, etc., are roughly divided into the dry development method and the wet development method, and the former is further divided into a method using a two-component developer and a method using a mono-component developer.
As toners used in the dry development methods, there have been used, e.g., fine particles of ca. 5-15 xcexcm, each comprising a binder resin and a colorant dispersed therein. In a magnetic toner as a mono-component developer, fine particles of a magnetic material are used as a colorant. On the other hand, a two component developer generally comprises a mixture of a toner containing carbon black, pigment, etc. as a colorant with carrier particles, such as iron powder or ferrite particles.
For imparting a charge to toner particles, a charge control agent, such as a dye, a pigment or a polymeric compound, is added. Examples of positive charge control agent include: nigrosine dyes, azine dyes, copper phthalocyanine pigment, and quaternary ammonium salts, and examples of negative charge control agents include organic metal compounds of monoazo dyes, organic metal compounds of salicylic acid, naphtoic acid and dicarboxylic acids, and polymers having a sulfonic acid group. However, the addition of such a charge control agent alone does not provide improvements in all developing performances, inclusive of sufficient image density, prevention of fog, etc.
It has been considered that the developing performances of a toner and the dielectric loss tangent (tanxcex4) are closely related. This is also true with respect to a toner comprising a sulfur-containing polymer.
Japanese Laid-Open Patent Application (JP-A) 6-118700 has disclosed a toner having a specified ratio between a peak tanxcex4 value in a high temperature region and a tanxcex4 in a normal temperature region so as to reduce image defects, such as fog. Such an improvement is not necessarily achieved with respect to a toner comprising a sulfur-containing polymer.
JP-A 7-191496 has disclosed a styrene-acrylic resin having a specified dielectric loss tangent (tanxcex4) as a toner binder having improved toner image density stability and chargeability. Such an improvement is not necessarily achieved with respect to a toner comprising a sulfur-containing polymer.
Japanese Patent (JP-B) 2596563 has disclosed a toner having a dielectric loss tangent (tanxcex4) within a specific range as a toner showing a proper image density. Such an improvement is not necessarily achieved with respect to a toner comprising a sulfur-containing polymer.
JP-A 11-295923 has disclosed a toner having a dielectric loss tangent (tanxcex4) of a specific value or smaller as a toner capable of suppressing fog. Such an improvement is not necessarily achieved with respect to a toner comprising a sulfur-containing polymer.
JP-A 63-184762 has disclosed a toner containing a copolymer of a specific acrylamide-sulfonic acid monomer for providing a stable chargeability. JP-A 2000-56518 has disclosed at toner containing a copolymer of a sulfonic acid group-containing (meth)acrylamide having a specific glass transition temperature as a charge control agent for provide a toner showing a stable chargeability with little dependence on the environmental conditions. However, these proposals have failed to disclose an optimum range of dielectric loss tangent for such toners containing a sulfur-containing polymer.
A generic object of the present invention is to provide a toner having solved the above-mentioned problems.
A more specific object of the present invention is to provide a toner improved in fog suppression, stability and environmental-dependence of chargeability and quick chargeability.
Another object of the present invention is to provide toner showing good fog suppression, stable chargeability, and a good combination of fixability and anti-high temperature-offset characteristic.
Another object of the present invention is to provide a toner capable of exhibiting improved resistance to toner offsetting onto a fixing member and a cleaning member regardless of the heating scheme of fixing devices.
Still another object of the present invention is to provide a toner containing a sulfur-containing polymer showing good dispersibility in a binder resin and capable of exhibiting good charge increase characteristic in an initial stage of image formation (quick chargeability) regardless of environmental conditions.
Further objects of the present invention are to provide an image forming method and a process cartridge using such a toner as described above.
According to the present invention, there is provided a toner, comprising toner particles each comprising at least a binder resin, a colorant and a wax, and inorganic fine powder, wherein
(a) the toner contains a sulfur-containing polymer, and
(b) the toner shows dielectric loss tangent (tanxcex4) values at 100 kHz assuming a maximum of 2.5xc3x9710xe2x88x922 to 8xc3x9710xe2x88x922 in a temperature range of 100 to 130xc2x0 C.
According to the present invention there is further provided an image forming method, comprising:
(i) a developing step of developing an electrostatic image held on an image-bearing member with a negatively chargeable toner to form a toner image thereon,
(ii) a transfer step of transferring the toner image formed on the image-bearing member onto a recording material via or without via an intermediate transfer member, and
(iii) a fixing step of heat-fixing the transferred toner image onto the recording material,
wherein the negatively chargeable toner comprises toner particles each comprising at least a binder resin, a colorant and a wax, and inorganic fine powder, wherein
(a) the toner contains a sulfur-containing polymer, and
(b) the toner shows dielectric loss tangent (tanxcex4) values at 100 kHz assuming a maximum of 2.5xc3x9710xe2x88x922 to 8xc3x9710xe2x88x922 in a temperature range of 100 to 130xc2x0 C.
The present invention further provides a process cartridge for use in an image forming apparatus of the type wherein an electrostatic image formed on an image-bearing member is developed with a toner transferred thereto to form a toner image and the toner image is transferred onto a recording material to form an image product,
wherein the process cartridge comprises at least one member selected from the group consisting of the image-bearing member, a charging means for charging the image-bearing member, a latent image forming means for forming the electrostatic image on the image-bearing member, a transfer means for transferring the toner image on the image-bearing member onto a recording material and a cleaning means for removing transfer residual toner remaining on the image-bearing member remaining after the transfer of the toner image, and a developing means for developing the electrostatic image on the image-bearing member with the above-mentioned toner to form the toner image on the image-bearing member supported integrally with said at least one member to form a unit which is detachably mountable to the image forming apparatus.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.